The present disclosure relates generally to a module or arrangement for, and a method of, illuminating a target to be electro-optically read by image capture and, more particularly, to uniformly and efficiently illuminate the target by generating an illumination light pattern that is substantially congruent to, and substantially overlaps, a field of view of an imaging reader.
Solid-state imaging systems or imaging readers have long been used, in both handheld and hands-free modes of operation, in many industries, such as retail, manufacturing, warehousing, distribution, postal, transportation, logistics, etc., to electro-optically read targets, such as one- or two-dimensional bar code symbols to be decoded. A known imaging reader generally includes an imaging module that is mounted in a housing, and that has an illumination light source for emitting illumination light over an illumination angle centered on an illumination axis toward a target for reflection and scattering therefrom, a solid-state imager with a sensor array of photocells or light sensors, and an optical assembly for capturing return illumination light scattered and/or reflected from the target being imaged over a field of view centered on an imaging axis, and for projecting the captured illumination light onto the imager to initiate capture of an image of the target. The imager produces electrical signals that are decoded and/or processed by a programmed microprocessor or controller into information related to the target being read, e.g., decoded data identifying the target. The controller is operative for transmitting the decoded data, either via a wireless or wired link, to a remote host for further processing, e.g., price retrieval from a price database to obtain a price for the identified target.
Although generally satisfactory for its intended purpose, the illumination light does not always uniformly and/or efficiently illuminate the targets over a broad range of working distances relative to the reader. Typical targets, such as bar code symbols, have lengths that are greater in dimension than their heights, and are therefore generally rectangular in shape. To best read such targets, the field of view of the imager is likewise generally rectangular in shape. For optimum reading performance, it would be desirable for the illumination light to not only be similarly configured with a generally rectangular illumination light pattern that has substantially the same size and same shape as, and that substantially overlaps, the generally rectangular field of view, but also be of uniform intensity over the field of view and to be efficiently transmitted with a maximum amount of illumination light to each target. In the prior art, however, this is not always achieved, primarily because the illumination light source and the imager are physically spaced apart and are horizontally and/or vertically offset from each other. In addition, their respective illumination and imaging axes are not collinear, but are typically inclined relative to, and intersect, each other. The typical illumination light pattern is non-uniform in intensity since the light intensity is brightest along the illumination axis on which the illumination light source is centered, and then falls off away from the illumination axis, especially at outer end regions of the illumination light pattern. Also, the typical illumination light pattern is mismatched, i.e., not substantially congruent, to the field of view, and the amount of illumination light delivered to each target is low, thereby resulting in a poor light transmission efficiency.
Accordingly, it would be desirable to more uniformly and more efficiently illuminate a target to be read by image capture by generating an illumination pattern that is substantially congruent to, and substantially overlaps, a field of view of an imaging reader.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and locations of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The module, arrangement and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.